In case people are wondering, it's as simple as parsing your own HTML pages for links, fetching those links, parsing the remote HTML for a webmention endpoint,

In case people are wondering, it's as simple as parsing your own HTML pages for links, fetching those links, parsing the remote HTML for a webmention endpoint, and if this exists, send a request over to it with headers indicating the URL of your own page, and the URL you linked to. The nature of the interaction is not contained within the webmention, but rather the site on the other site will fetch and parse your page to figure that out. That information is within the HTML itself, such as `<a class="u-in-reply-to" href="foo.bar/baz">Commenting on this article</a>` to express a commenting/reply relationship.